import java.util.Arrays;

public class Test {
    public static void main(String[] args) {
        int[] arr=new int[]{1,2,3};
        System.out.println("改变前arr为"+Arrays.toString(arr));
        System.out.println("改变后arr为"+Arrays.toString(num(arr)));

    }
    public static int[] num(int[] arr){
        for(int i=0;i<arr.length;i++){
            arr[i]*=2;
        }
        return arr;
    }
}
